Two-stroke performance tuning?

[SS90]

I think there are a few but keeping it topical, any post where you claim that there is no supercharging effect from the expansion chamber.

A lot of literature says there is.

You will need to do better than a "because I say so approch". A coherent well thought out illustrated explination of your view could change my mind, untill then I have to hold to the conventional wisdom.

In holding to the conventional wisdom, its not for me to prove you wrong. Its for you to explain yourself in a way that allows me to see your right.

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Teezee,

I have already conceded there is a "supercharging effect" caused by the expansion chamber (actually I have never claimed there wasn't)

However, what I am saying is that " A conventional normally aspirated two stroke engine IS NOT "supercharged"

A "supercharge effect" does not constitute a "supercharged engine" anymore than an air box does.

Do you know of any literature that shows that an expansion chamber "supercharges" a cylinder (not just provides a supercharge effect)

I don't feel I am arguing over semantics.

These are important differences. (supercharge effect, opposed to actually being "supercharged"

Fooman posted above on what is considered "supercharged"

We have already established that simply increasing VE is NOT supercharging (or else power valves would be considered "mechanical superchargers"), or in the case of a 4 stroke, multiple valves (which also increase VE)

So, an expansion chamber will increase the VE of a two stroke engine......(so done by applying a "dynamic supercharger effect")

That doesn't make it "supercharged"

[CookMySock]

That doesn't make it "supercharged"

It's pretty clear the cylinder has a greater-than-atmo charge in it.

What shall we call it then? Pseudo-supercharged? Supercharged but not quite? *****charged? PosVEcharged?

You should become a patent attorney.

Steve

[TZ350]

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The advantage of a mechanical supercharger is that it delivers over a wide rev range where as a resenant supercharger like an expansion chamber, only works over a limited rev range.

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[SS90]

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The advantage of a mechanical supercharger is that it delivers over a wide rev range where as a resenant supercharger like an expansion chamber, only works over a limited rev range.

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Hang on,

But have you got any literature to show that it actually "supercharges" a cylinder?

Supercharging effect yes, does this "supercharge" the cylinder?.......no.

[SS90]

It's pretty clear the cylinder has a greater-than-atmo charge in it.



Steve

Greater than atmosphere charge?
Every internal combustion engine has greater than atmosphere charge in it.

Erm, does that make it supercharged?

Fooman posted above what constitutes a supercharged engine.

[TZ350]

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Supercharging effect yes, does this "supercharge" the cylinder?.......no.
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SS don't lose sight of the fact that the expansion chamber does more than supercharge the cylinder.

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[SS90]

SS don't lose sight of the fact that the expansion chamber does more than supercharge the cylinder.

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Erm, Yes Teezee I am quite aware of that.

However, I feel it is important to understand how an expansion chamber works "piece by piece" (as it where) so we all can get a better understanding of things.

That's why I post on this site.

[bucketracer]

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Ok Skunk, I have posted this run in the ESE thread, but here is an example of how an expansion chamber DOES NOT "SUPERCHARGE" a cylinder.

The same exhaust,head,primary compression,ignition (and timing) flywheel etc.....

Only the scavenge pattern has been changed (dramatically).........

If a two stroke chamber "supercharged" a cylinder, why would keeping the air/fuel mixture in the cylinder (stopping it heading out the open exhaust port) make such an improvement?

This graph shows otherwise.
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If TZ350 posted this he would have shown us drawings of the before and after pattern and an explination of how the changes better prevents the mixture heading out the exhaust.

Without an explination your graph is just a picture with lines.

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[SS90]

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If TZ350 posted this he would have shown us drawings of the before and after pattern and an explination of how the changes better prevents the mixture heading out the exhaust.

Without an explination your graph is just a picture with lines.

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With my heart in my mouth just replying to you Bucketracer (and expecting the usual abuse) I'll give it a shot.

The fact is that Teezee didn't post anything about scavenge patterns, because in the ESE thread, he was unaware of the concept.

Don't take that as an insult, it's just a fact.

I pointed him in the direction of Honda RS125's, (and their scavenge patterns) as a VERY good place too start (however, I would not recommend copying them for a disc valve two stroke, but it is a good place to learn)

Yes, he went to the effort of measuring them, then posting them. Good for him.

I won't simply post designs or important specs that I use, however I will attempt to generate conversation so we can all learn and expand our knowledge, and PERHAPS we can all improve our ideas.

[gav]

What was the chamber? I will sell you one for €500 (incl postage), it will only fit a small frame Vespa (sorry) But it will be hand made in Germany (by a Kiwi)

Was there a chamber? errrr YES.

What did I do to achieve the scavenge effect? Paid attention and accepted advise from people, along with intelligent conversation and constructive critisisim, along with leaning "how and why" other manufacturers did things.

I don't say that the chamber was doing absolutely "nothing", I use this as an example to show that if the chamber was "supercharging" the cylinder, then improvements in the scavenge patterns would have no effect.

Have you got a chart to show this same engine being run with a standard exhaust and then a chamber so we can see the difference that the chamber makes (or not ) to the engine?

[Skunk]

Does an expansion chamber "supercharge" a cylinder?

NO.

I have already said it was a throw away term to loosely describe one effect of a chamber. I note you have gone to great lengths to say I'm wrong (which in specific terminology I am) but haven't said anything about why it's wrong and clearly explain anything about what is going.
I even asked you directly and you avoid answering.

In regards to the supercharging, yes, I agree, it's a terminology thing.

Oh, really?

But have you got any literature to show that it actually "supercharges" a cylinder?

Your evidence is?...

I won't simply post designs or important specs that I use, however I will attempt to generate conversation so we can all learn and expand our knowledge, and PERHAPS we can all improve our ideas.

Now would be a good time to start. I haven't seen any 'knowledge' from you and we're a few pages into this thread now...

[bucketracer]

With my heart in my mouth just replying to you Bucketracer (and expecting the usual abuse) I'll give it a shot.

The fact is that Teezee didn't post anything about scavenge patterns, because in the ESE thread, he was unaware of the concept.

I doubt that he was unaware of the concept, you assume too much.

And from the last few pages can you give me an example of my abuse, I can certainly show you many examples of yours including much childishness.

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[F5 Dave]

Re Sketchy;

. . .
It's something we all have done, but some experience would have told him that it was "off"


For example, you need ALOT more information to design an expansion chamber than simply exhaust port specs and intended RPM range.

I don't think Sketchy claims to have much experience, but he is learning. I certainly didn't know anywhere near as much at 19. & I doubt you did either. His approach has been fairly well researched, methodical & definitely enthusiastic.

None of which changes his observation. Your acidic and argumentative personality totally prevents you from playing well with others. I'm hardly surprised you are getting the flack you are. And I bet it has affected your ability to learn as winning the argument seems the most important thing,


. . . even if you can't convince others that you have won.

[bucketracer]

Yes, he went to the effort of measuring them, then posting them. Good for him.

I won't simply post designs or important specs that I use, however I will attempt to generate conversation so we can all learn and expand our knowledge, and PERHAPS we can all improve our ideas.

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Yes and good for us.

TZ does not post designs or important specs either

but he does explain important concepts very well with drawings Etc so you can design your own.

And he is totaly open with sharing his knowledge and allways acknowledges sources like Thomas yourself and others.

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[Buckets4Me]

I have already conceded there is a "supercharging effect" caused by the expansion chamber (actually I have never claimed there wasn't)

However, what I am saying is that " A conventional normally aspirated two stroke engine IS NOT "supercharged"

A "supercharge effect" does not constitute a "supercharged engine" anymore than an air box does.

These are important differences. (supercharge effect, opposed to actually being "supercharged"

I'm getting more and more confused

so if you ram more air (and fuel) into an engine you can call it a supercharger affect but not supercharged ????

and also if the chamber dosent ram more air into the engine than it would have had without it then what dose it do ????

someone answer me come on

NOS is not supercharging the engine watchout TAUPO
I'm going to beat you all to the first corner
then I'm going to brake realy hard so you all had better give me lots a room
then I'm going to beat you all up the hill (and brake hard again)
then I'm going to cost down the hill braking hard and early (I'm to scared to realy gass it out there)
and beat you all up the hill again